<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>尹旭冉的博客</title>
    <style>
      html {
        height: 900px;
      }
      body {
        margin: 0;
        height: 100%;
        background: #fff;
      }
      canvas {
        position: fixed;
        z-index: -2;
        display: block;
        width: 100%;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <canvas id="canvas"></canvas>
    <div id="app"></div>
  </body>
  <script>

    class Circle {
      //创建对象
      //以一个圆为对象
      //设置随机的 x，y坐标，r半径，_mx，_my移动的距离
      //this.r是创建圆的半径，参数越大半径越大
      //this._mx,this._my是移动的距离，参数越大移动
      constructor(x, y) {
        this.x = x;
        this.y = y;
        this.r = Math.random() * 10;
        this._mx = Math.random();
        this._my = Math.random();
  
      }
  
      //canvas 画圆和画直线
      //画圆就是正常的用canvas画一个圆
      //画直线是两个圆连线，为了避免直线过多，给圆圈距离设置了一个值，距离很远的圆圈，就不做连线处理
      drawCircle(ctx) {
        ctx.beginPath();
        //arc() 方法使用一个中心点和半径，为一个画布的当前子路径添加一条弧。
        ctx.arc(this.x, this.y, this.r, 0, 360)
        ctx.closePath();
        ctx.fillStyle = 'rgba(204, 204, 204, 0.3)';
        ctx.fill();
      }
  
      drawLine(ctx, _circle) {
        let dx = this.x - _circle.x;
        let dy = this.y - _circle.y;
        let d = Math.sqrt(dx * dx + dy * dy)
        if (d < 150) {
          ctx.beginPath();
          //开始一条路径，移动到位置 this.x,this.y。创建到达位置 _circle.x,_circle.y 的一条线：
          ctx.moveTo(this.x, this.y); //起始点
          ctx.lineTo(_circle.x, _circle.y); //终点
          ctx.closePath();
          ctx.strokeStyle = 'rgba(204, 204, 204, 0.3)';
          ctx.stroke();
        }
      }
  
      // 圆圈移动
      // 圆圈移动的距离必须在屏幕范围内
      move(w, h) {
        this._mx = (this.x < w && this.x > 0) ? this._mx : (-this._mx);
        this._my = (this.y < h && this.y > 0) ? this._my : (-this._my);
        this.x += this._mx / 2;
        this.y += this._my / 2;
      }
    }
  
    //鼠标点画圆闪烁变动
    class currentCirle extends Circle {
      constructor(x, y) {
        super(x, y)
      }
  
      drawCircle(ctx) {
        ctx.beginPath();
        //注释内容为鼠标焦点的地方圆圈半径变化
        //this.r = (this.r < 14 && this.r > 1) ? this.r + (Math.random() * 2 - 1) : 2;
        this.r = 8;
        ctx.arc(this.x, this.y, this.r, 0, 360);
        ctx.closePath();
        //ctx.fillStyle = 'rgba(0,0,0,' + (parseInt(Math.random() * 100) / 100) + ')'
        ctx.fillStyle = 'rgba(255, 77, 54, 0.6)'
        ctx.fill();
  
      }
    }
  
    //更新页面用requestAnimationFrame替代setTimeout
    window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
  
    let canvas = document.getElementById('canvas');
    let ctx = canvas.getContext('2d');
    let w = canvas.width = canvas.offsetWidth;
    let h = canvas.height = canvas.offsetHeight;
    let circles = [];
    let current_circle = new currentCirle(0, 0)
  
    let draw = function() {
      ctx.clearRect(0, 0, w, h);
      for (let i = 0; i < circles.length; i++) {
        circles[i].move(w, h);
        circles[i].drawCircle(ctx);
        for (j = i + 1; j < circles.length; j++) {
          circles[i].drawLine(ctx, circles[j])
        }
      }
      if (current_circle.x) {
        current_circle.drawCircle(ctx);
        for (var k = 1; k < circles.length; k++) {
          current_circle.drawLine(ctx, circles[k])
        }
      }
      requestAnimationFrame(draw)
    }
  
    let init = function(num) {
      for (var i = 0; i < num; i++) {
        circles.push(new Circle(Math.random() * w, Math.random() * h));
      }
      draw();
    }
  
    window.addEventListener('load', init(60));
  
    window.onmousemove = function(e) {
      e = e || window.event;
      current_circle.x = e.clientX;
      current_circle.y = e.clientY;
    }
  
    window.onmouseout = function() {
      current_circle.x = null;
      current_circle.y = null;
    }
  </script>
</html>
